The present invention relates logic signal translator circuits and, more particularly, to a BICMOS translator circuit for translating ECL input signals to CMOS logic level output signals.
There is a myriad of prior art logic signal level translator which are responsive to logic input signal of a first logic level for providing output logic signals compatible to a second logic level. For example, a typical logic circuit may receive ECL inputs signals which switch between 0.0 and -0.8 volts representative of a logic one and logic zero accordingly. The output of the logic circuit may have to drive CMOS logic circuitry that requires logic signal swings between 0.0 and -5.2 volts (typical) for operation. Thus, the ECL signal level must be translated to the greater CMOS logic signal voltage swing which requires the use of translator circuitry.
Prior art ECL to CMOS logic voltage level translator circuits are known in the art. For instance, U.S. Pat. No. 4,644,194 as well as a patent application entitled, "HIGH SPEED ECL TO CMOS TRANSLATOR HAVING REDUCED POWER CONSUMPTION", Ser. No. 445,529, assigned to Motorola, Inc. disclose such translators to which the subject invention is related. Although, prior art translator circuits work reasonably well they may suffer from several disadvantages to which the subject application addresses. Most, if not all, prior art translator circuits for driving CMOS logic circuitry from a different input logic level require some sort of buffer circuit to isolate the translator from the load. In general, the need for a buffer circuit increases switching time delays which is undesirable. In addition, prior art translator circuits of the type mentioned above may suffer in performance due to substantial variations in the power supply voltage and temperature.
Hence, a need exists for a high speed ECL to CMOS logic voltage translator which is independent to variation in power supply voltage levels and temperature which does not require buffer circuitry between the output thereof and the CMOS load that is driven therefrom.